Thermal Stability and Topological Charge Fragmentation in Antiskyrmions of Rhombohedral Barium Titanate

Abstract

Antiskyrmions, as topological quasi-particles, hold significant promise for spintronics and nanoscale data storage applications. Using molecular dynamics simulations based on effective Hamiltonians, we investigate the thermal stability of antiskyrmion nanodomains in rhombohedral barium titanate. At 1 K, antiskyrmions with a topological charge of -2 emerge as the most stable nanodomain state across all examined diameters. In our systematic study, the most robust antiskyrmion was found to have a diameter of 4 nm, maintaining its original size, shape, and topological charge up to the characteristic temperature T* ~ 85 K. Domains with diameters between 2.8 and approximately 4.5 nm exhibit fragmentation into six topological defects, termed quarks, each carrying a fractional skyrmion charge of -1/3. For domains larger than 4.5 nm, each topological quark splits into two pre-quarks, each with a charge of -1/6. These larger nanodomains demonstrate increased mobility and a growing tendency for shape and skyrmion charge fluctuations. Above the T* temperature, all larger nanodomains gradually shrink to a diameter of about 4 nm before collapsing into a single-domain state. These findings reveal the relatively high stability of antiskyrmions over a broad temperature range, even in the absence of a stabilizing bias field, and emphasize the pivotal role of topological quark dynamics. This establishes barium titanate as a key platform for exploring and applying topological phenomena.